Microgel-containing vulcanizable composition based on hydrogenated nitrile rubber

ABSTRACT

A novel vulcanizable composition is provided, based on at least one hydrogenated nitrile rubber, on at least one peroxide, on at least one unsaturated carboxylic acid and/or salts thereof, and also on specific microgels. These vulcanizable compositions can be used to obtain vulcanized products which can in particular be used for drive belts, roll coverings, hoses and cables.

FIELD OF THE INVENTION

The present invention relates to a microgel-containing vulcanizablecomposition based on hydrogenated nitrile rubber and to its preparation,and moreover to vulcanized products produced therefrom and to their usein particular in drive belts, in roll coverings, in gaskets, in hosesand in cables.

BACKGROUND OF THE INVENTION

The production of vulcanized rubber items based on hydrogenated nitrilerubbers is known in particular for drive belts, roll coverings, gaskets,hoses and cables. If the items based on partially hydrogenated nitrilerubbers are produced via sulphur vulcanization according to DE-A-29 13992 or EP-A-0 265 706, the properties of these rubber items then becomeinadequate in particular at the high temperatures nowadays encounteredin various applications. Vulcanisates with better ageing resistance areobtained on the basis of more highly hydrogenated nitrile rubbers whichare vulcanized with sulphur according to EP-A-0 112 109, or with the aidof organic peroxides according to DE-A-34 38 414, or else with inorganicperoxides according to EP-A-0 383 127. However, the hardness and alsothe tensile stress values at various tensile strain values can still beimproved, both at room temperature and at higher temperatures, forexample at 130° C. Additions of salts of unsaturated carboxylic acids isa successful method in the case of peroxidically vulcanized nitrilerubbers for improving hardness and the level of modulus, both at roomtemperature and at 130° C. The salts of the unsaturated carboxylic acidshere can be prepared “in situ” (U.S. Pat. No. 5,391,627) duringpreparation of the compounded material from the oxides and thecorresponding unsaturated carboxylic acids. However, according to U.S.Pat. No. 5,208,294 it is also possible to add the salts of theunsaturated carboxylic acids directly. In this case, the salts of theunsaturated carboxylic acids are prepared in a separate step of aprocess or are purchased.

However, with the aim of further improvement in the property profile ofvulcanized rubber items based on hydrogenated nitrile rubbers, inparticular for use in drive belts, in rolls, in gaskets, in hoses and incables, a further improvement in mechanical properties is desirable andspecifically also at high temperatures of 130° C. or above, these beingtemperatures that can particularly and increasingly arise in automobileapplications. The intention is that this improved property profile is tobe retained even over a prolonged period of storage at thesetemperatures. However, at the same time the intention is that rubberitems improved in this way have unaltered good hardness values.

The use of rubber gels, also termed microgels, is known for underlyingcontrol of the properties of vulcanisates (e.g. EP-A-0 405 216, DE-A 4220 563, GB Patent 1078400, DE-A-197 01 487, DE-A-197 01 489, DE-A-197 01488, DE-A-198 34 804, DE-A-198 34 803, DE-A-198 34 802, EP-A-1 063 259,DE-A-199 39 865, DE-A-199 42 620, DE-A-199 42 614, DE-A-100 21 070,DE-A-100 38 488, DE-A-100 39 749, DE-A-100 52 287, DE-A-100 56 311 andDE-A-100 61 174). These specifications disclose improvement of variousvulcanisate properties via additions of microgels, but not with thefocus on high-temperature applications.

SUMMARY OF THE INVENTION

The object of the present invention consisted in providing vulcanisateswhich are based on hydrogenated nitrile rubbers and which have markedlyimproved mechanical properties, in particular at high temperatures, suchas 130° C., and also after storage in hot air at 150° C.

Surprisingly, this object could be achieved by starting from avulcanizable composition which is based on a combination composed of ahydrogenated nitrile rubber, of an unsaturated carboxylic acid or of asalt thereof, of a peroxide and of specific microgels.

DETAILED DESCRIPTION OF THE INVENTION

The invention therefore provides vulcanizable compositions comprising

-   -   a) one or more hydrogenated nitrile rubbers,    -   b) one or more unsaturated carboxylic acids and/or one or more        salts thereof,    -   c) at least one peroxide and    -   d) at least one microgel whose glass transition temperature is        below −20° C.

This method of achieving the object was surprising insofar as microgelswhose glass transition temperature is below −20° C. are prepared usingdienes, such as butadiene, isoprene, inter alia and therefore containdouble bonds which are susceptible to ageing processes. According toASTM D2000, it is to be expected that use of double-bond-containingrubber gels (the materials known as “R rubbers”) is likely to impairageing resistance at 150° C., since according to ASTM D2000 a maximumuse temperature <100° C. is to be assumed for double-bond-containingrubber gels.

However, when the specific microgels are used in the inventivevulcanizable compositions the level of mechanical properties of thecorresponding vulcanisates is markedly improved both at an operatingtemperature of 130° C. and after storage in hot air at 150° C. Theseimprovements are not possible when using the vulcanizable compositionsknown hitherto of hydrogenated nitrile rubbers, which comprise nomicrogels. For example, no property improvement at high temperatures isachieved in a composition of this type solely via an increase in theamount of zinc diacrylate. The result when the inventive compositionsare used is not only the property improvement at high temperatures butalso retention of unaltered good mechanical properties at roomtemperature, and high hardness values at low density.

The inventive compositions moreover lead to advantages in relation tothe production process for the vulcanized products. The vulcanizedproducts are often produced by way of injection-moulding processes. Thevulcanisates of the inventive microgel-containing compositions here haveless tack and are therefore easier to demould, and this leads to lessmould soiling in the production process. The inventivemicrogel-containing compositions moreover give an unaltered scorch time(e.g. t₁₀) with, simultaneously, a short full-vulcanization time (t₉₀and t₉₅).

Hydrogenated Nitrile Rubbers:

For the purposes of this application, hydrogenated nitrile rubbers areco- and/or terpolymers based on at least one conjugated diene and on atleast one α,β-unsaturated nitrile monomer and also if appropriate onother copolymerizable monomers, in which the diene units incorporatedinto the polymer have been entirely or to some extent hydrogenated. Thedegree of hydrogenation of the diene units incorporated into the polymeris usually in the range from 50 to 100%, preferably in the range from 85to 100% and particularly preferably in the range from 95 to 100%.

The conjugated diene can be of any type. It is preferable to use (C₄-C₆)conjugated dienes. Particular preference is given to 1,3-butadiene,isoprene, 2,3-dimethylbutadiene, piperylene or a mixture thereof.Particular preference is given to 1,3-butadiene and isoprene or amixture thereof. 1,3-butadiene is very particularly preferred.

The α,β-unsaturated nitrile used can comprise any known α,β-unsaturatednitrile, and preference is given to (C₃-C₅) α,β-unsaturated nitriles,such as acrylonitrile, methacrylonitrile, ethacrylonitrile or a mixtureof these. Acrylonitrile is particularly preferred.

Other copolymerizable monomers are unsaturated carboxylic acids, andalso the esters of the unsaturated carboxylic acids.

The unsaturated carboxylic acids are preferably mono- or dicarboxylicacids having from 3 to 16 carbon atoms, with α,β-unsaturation. Examplesof the α,β-unsaturated carboxylic acids are: acrylic acid, methacrylicacid, itaconic acid, fumaric acid, maleic acid, crotonic acid andmixtures thereof.

Esters of the α,β-unsaturated carboxylic acids having from 3 to 16carbon atoms preferably encompass the alkyl esters and the alkoxyalkylesters of the abovementioned carboxylic acids. Preferred esters of theα,β-unsaturated carboxylic acids having from 3 to 16 carbon atoms aremethyl acrylate, ethyl acrylate, butyl acrylate, 2-ethylhexyl acrylateand octyl acrylate. Preferred alkoxyalkyl esters are methoxyethylacrylate, ethoxyethyl acrylate and methoxyethyl acrylate, and alsomixtures of the same.

The proportions of conjugated diene and of α,β-unsaturated nitrile inthe hydrogenated nitrile rubbers can be varied widely. The proportion ofthe conjugated diene or of the entirety of the conjugated dienes isusually in the range from 40 to 90% by weight and preferably in therange from 50 to 80% by weight, based on the entire polymer. Theproportion of the α,β-unsaturated nitrile or of the entirety of theα,β-unsaturated nitriles is usually from 10 to 60% by weight, preferablyfrom 20 to 50% by weight, based on the entire polymer. The amounts thatcan be present of the additional monomers are from 0.1 to 40% by weight,preferably from 1 to 30% by weight, based on the entire polymer. In thiscase, corresponding proportions of the conjugated diene(s) and/or of theα,β-unsaturated nitrile(s) are replaced via the proportions of theadditional monomers, and the proportions of all of the monomers here ineach case give a total of 100% by weight.

The preparation of hydrogenated nitrile rubbers of this type which aresuitable for the inventive vulcanizable compositions is very familiar tothe person skilled in the art.

The initial preparation of the nitrile rubbers via polymerization of theabovementioned monomers is extensively described in the literature (e.g.Houben-Weyl, Methoden der Organischen Chemie [Methods of organicchemistry], Vol. 14/1, Georg Thieme Verlag Stuttgart 1961).

The subsequent hydrogenation of the nitrile rubbers described above togive hydrogenated nitrile rubber can take place in the manner known tothe person skilled in the art. By way of example, a suitable method isreaction with hydrogen with use of homogeneous catalysts, e.g. thecatalyst known as “Wilkinson” catalyst ((PPh₃)₃RhCl) or others.Processes for the hydrogenation of nitrile rubber are known. Rhodium ortitanium are usually used as catalysts, but platinum, iridium,palladium, rhenium, ruthenium, osmium, cobalt or copper can also be usedeither in the form of metal or else preferably in the form of metalcompounds (see, for example, U.S. Pat. No. 3,700,637, DE-A-2 539 132,EP-A-134 023, DE-A-35 41 689, DE-A-35 40 918, EP-A-298 386, DE-A-35 29252, DE-A-34 33 392, U.S. Pat. No. 4,464,515 and U.S. Pat. No.4,503,196).

Suitable catalysts and solvents for homogeneous-phase hydrogenation aredescribed below and are also disclosed in DE-A-25 39 132 and EP-A-0 471250.

Selective hydrogenation can be achieved, for example, in the presence ofa rhodium-containing catalyst. By way of example, a catalyst of thegeneral formula(R¹ _(m)B)_(l)RhX_(n)can be used, in which

-   R¹ are identical or different and are a C₁-C₈-alkyl group, a    C₄-C₈-cycloalkyl group, a C₆-C₁₅-aryl group or a C₇-C₁₅-aralkyl    group,-   B is phosphorus, arsenic, sulphur or a sulphoxide group S═O,-   X is hydrogen or an anion, preferably halogen and particularly    preferably chlorine or bromine,-   l is 2, 3 or 4,-   m is 2 or 3 and-   n is 1, 2 or 3, preferably 1 or 3.

Preferred catalysts are tris(triphenylphosphine)rhodium(I) chloride,tris(triphenylphosphine)rhodium(III) chloride and tris(dimethylsulphoxide)rhodium(III) chloride, and alsotetrakis(triphenylphosphine)rhodium hydride of the formula((C₆H₅)₃P)₄RhH and the corresponding compounds in which thetriphenylphosphine has been entirely or to some extent replaced bytricyclohexylphosphine. Small amounts of the catalyst can be used. Asuitable amount is in the range from 0.01 to 1% by weight, preferably inthe range from 0.03 to 0.5% by weight and particularly preferably in therange from 0.1 to 0.3% by weight, based on the weight of the polymer.

It is usually advisable to use the catalyst together with a co-catalystwhich is a ligand of the formula R¹ _(m)B, where R¹, m and B are asdefined above for the catalyst. m is preferably equal to 3, B ispreferably equal to phosphorus, and the radicals R¹ can be identical ordifferent. The co-catalysts preferably have trialkyl, tricycloalkyl,triaryl, triaralkyl, diarylmonoalkyl, diarylmonocycloalkyl,dialkylmonoaryl, dialkylmonocycloalkyl, dicycloalkylmonoaryl ordicycloalkylmonoaryl radicals.

Suitable co-catalysts are found by way of example in U.S. Pat. No.4,631,315. Triphenylphosphine is preferred co-catalyst. The amounts usedof the co-catalyst are preferably from 0.3 to 5% by weight, preferablyin the range from 0.5 to 4% by weight, based on the weight of thenitrile rubber to be hydrogenated. The ratio by weight of therhodium-containing catalyst to the co-catalyst is moreover preferably inthe range from 1:3 to 1:55, preferably in the range from 1:5 to 1:45. Asuitable method uses from 0.1 to 33 parts by weight of the co-catalyst,preferably from 0.5 to 20 parts by weight and particularly preferablyfrom 1 to 5 parts by weight, in particular more than 2 but less than 5parts by weight, of co-catalyst, based on 100 parts by weight of thenitrile rubber to be hydrogenated.

The practical method for these hydrogenations is well known to theperson skilled in the art from U.S. Pat. No. 6,683,136, for example. Inthe usual method, the nitrile rubber to be hydrogenated is treated withhydrogen in a solvent such as toluene or monochlorobenzene at atemperature in the range from 100 to 150° C. and at a pressure in therange from 50 to 150 bar for from 2 to 10 h.

The Mooney viscosity of the hydrogenated nitrile rubbers used in theinventive process (ML 1+4 @ 100° C.) is in the range from 10 to 120 MU,preferably in the range from 15 to 100 MU, where the Mooney viscosity isdetermined to ASTM standard D1646.

Hydrogenated nitrile rubbers of this type are commercially available.Examples of hydrogenated nitrile rubber are fully and partiallyhydrogenated nitrile rubbers with acrylonitrile contents in the rangefrom 20 to 50% by weight (Therban® range from Lanxess Deutschland GmbH,and also Zetpol® range from Nippon Zeon Corporation). Examples ofhydrogenated butadiene-acrylonitrile-acrylate polymers are the Therban®LT range from Lanxess Deutschland GmbH, e.g. Therban® LT 2157, and alsoTherban® VP KA 8882. An example of carboxylated hydrogenated nitrilerubber is the Therban® XT range from Lanxess Deutschland GmbH. Examplesof hydrogenated nitrile rubbers with low Mooney viscosities andtherefore with improved processability are products from the Therban® ATrange, e.g. Therban AT VP KA 8966.

Unsaturated Carboxylic Acids and/or One or More Salts Thereof:

The inventive vulcanizable composition comprises one or more unsaturatedcarboxylic acids and/or one or more salts thereof. This component isconcomitantly incorporated to some extent into the network duringsubsequent peroxidic vulcanization. The unsaturated carboxylic acid ispreferably an α,β-ethylenically unsaturated mono- or dicarboxylic acidhaving from 3 to 10 carbon atoms, e.g. acrylic acid, methacrylic acid,cinnamic acid, crotonic acid or itaconic acid. Acrylic acid andmethacrylic acid are particularly preferred. Suitable metal salts arethose of sodium, potassium, magnesium, calcium, zinc, barium, aluminium,tin, zirconium, lithium. Sodium, zinc, magnesium and aluminium areparticularly preferred. Metal diacrylates are particularly preferred, inparticular zinc diacrylate, and metal dimethacrylates, in particularzinc dimethacrylate.

Based on 100 pars by weight of the hydrogenated nitrile rubbers theinventive compositions preferably use from 1 to 100 parts by weight,more preferably from 5 to 80 parts by weight of the unsaturatedcarboxylic acids and/or one or more salts thereof, preferably of theα,β-ethylenically unsaturated mono- or dicarboxylic acids having from 3to 10 carbon atoms or of one or more salts thereof. According to theinvention it is also possible to prepare the salt(s) of theα,β-unsaturated mono- or dicarboxylic acid(s) during the preparation ofthe inventive vulcanizable composition (“compounding”) or duringsubsequent vulcanization “in situ”.

Peroxide:

The inventive vulcanizable composition moreover comprises at least oneperoxide preferably selected from organic peroxides, in particular beingdicumyl peroxide, tert-butyl-cumyl peroxide,bis(tert-butylperoxyisopropyl)benzene, di-tert-butyl peroxide,2,5-dimethylhexane 2,5-dihydroperoxide, 2,5-dimethylhex-3-yne2,5-dihydroperoxide, dibenzoyl peroxide,bis(2,4-dichlorobenzoyl)peroxide, tert-butyl perbenzoate, butyl4,4-di(tert-butylperoxy)valerate or1,1-bis(tert-butylperoxy)-3,3,5-trimethylcyclohexane. However, it isalso possible to use the peroxides mentioned at a later stage below formicrogel preparation. The total amount of the peroxide(s) used ispreferably from 0.2 to 8 parts by weight, particularly preferably from0.2 to 5 parts by weight, in particular from 0.2 to 4 parts by weight,based on 100 parts by weight of the hydrogenated nitrile rubbers.

Microgel Whose Glass Transition Temperature is Below −20° C.:

The glass transition temperature of the microgels that can be used inthe inventive vulcanizable composition is below −20° C.

The microgel used in the inventive vulcanizable composition is usually acrosslinked microgel based on homopolymers or on random copolymers. Theinventively used microgels are therefore usually crosslinkedhomopolymers or crosslinked random copolymers. The expressionshomopolymers and random copolymers are well known to the person skilledin the art and are explained by way of example in Vollmert, PolymerChemistry, Springer 1973.

The glass transition temperatures of the microgels are generally higherby from 1° C. to 10° C. than the glass transition temperatures of thecorresponding non-crosslinked homo- or copolymers, and, to a firstapproximation, the glass transition temperatures of the microgels hererise proportionally with the degree of crosslinking. In the case ofweakly crosslinked microgels, the glass transition temperatures arehigher only by about 1° C. than those of the corresponding homo- orcopolymers. In the case of highly crosslinked microgels, the glasstransition temperatures can be higher by up to 10° C. than the glasstransition temperatures of the corresponding non-crosslinked homo- orcopolymers. The glass transition temperatures of the underlyingnon-crosslinked copolymers can be calculated (Vollmert, PolymerChemistry, Springer 1973) with the aid of the Gordon-Taylor relationshipor of the Fox-Flory relationship. These calculations give good resultsif the following glass transition temperatures of the correspondinghomopolymers are input: polybutadiene: −80° C., polyisoprene: −65° C.,polychloroprene: −39° C., polystyrene: 100° C. and polyacrylonitrile100° C.

The microgels used in the inventive vulcanizable compositionadvantageously have at least 70% by weight of fractions (“gel content”)insoluble in toluene at 23° C., preferably at least 80% by weight, andparticularly preferably at least 90% by weight. This fraction insolublein toluene is determined in toluene at a temperature of 23°. 250 mg ofthe microgel are swollen here in 25 ml of toluene at 23° C. for 24hours, with shaking. After centrifuging at 20 000 rpm, the insolublefraction is isolated and dried. The gel content is found by taking thequotient of the dried residue and the starting weight and is stated inpercent by weight.

The microgels used in the inventive vulcanizable composition usuallyhave a swelling index (“SI”) in toluene at 23° C. of less than 80,preferably less than 60 and in particular less than 40. The swellingindex of the microgels is particularly preferably in the range from 1 to30, in particular in the range from 1 to 20. The swelling index SI iscalculated from the weight of the solvent-containing microgel swollenfor 24 hours in toluene at 23° C. (after centrifuging at 20 000 rpm) andthe weight of the dry microgel by using the following formula:SI=wet weight of microgel/dry weight of microgel.

To determine the swelling index, 250 mg of the microgel are allowed toswell in 25 ml of toluene for 24 h, with shaking. The gel is removed bycentrifuging and weighed and is then dried to constant weight at 70° C.and again weighed.

The glass transition temperatures T_(g) of the microgels used in theinventive vulcanizable composition are preferably in the range from−100° C. to −20° C., particularly preferably in the range from −80° C.to −20° C. and in particular in the range from −80° C. to −50° C.

The width of the glass transition (“ΔT_(g)”) of the microgels used isusually moreover greater than 5° C., preferably greater than 10° C.,particularly preferably greater than 20° C. Microgels having this widthof glass transition are generally unlike completely homogeneousmicrogels obtained, for example, via radiation crosslinking, in nothaving completely homogeneous crosslinking. A consequence of this isthat the change in modulus from the matrix phase to the disperse phaseis not immediate. A result of this in the event of sudden stress is thatbreak-away effects do not occur between matrix and disperse phase, andthere is a resultant favourable effect on mechanical properties,swelling behaviour and buckling behaviour.

The glass transition temperature (T_(g)) of the microgels and the widthof their glass transition (ΔT_(g)) are determined by means ofdifferential scanning calorimetry (DSC). To determine T_(g) and ΔT_(g),two cooling/heating cycles are carried out. T_(g) and ΔT_(g) aredetermined in the second heating cycle. For the determinations, 10-12 mgof the selected microgel are placed in a Perkin-Elmer DSC specimencontainer (standard aluminium dish). The first DSC cycle is carried outby first cooling the specimen with liquid nitrogen to −100° C. and thenheating it at a rate of 20 K/min to +150° C. The second DSC cycle isbegun by immediate cooling of the specimen as soon as a specimentemperature of +150° C. has been reached. The cooling rate used is about320 K/min. In the second heating cycle, the specimen is again heated asin the first cycle to +150° C. The heating rate in the second cycle isagain 20 K/min. T_(g) and ΔT_(g) are determined graphically on the DSCcurve for the second heating procedure. To this end, three straightlines are drawn on the DSC curve. The 1st straight line is drawn on thatsection of the DSC curve below T_(g), the 2nd straight line is drawn onthat part of the curve running through T_(g) with an inflection point,and the 3rd straight line is drawn on that part of the DSC curve aboveT_(g). This method gives three straight lines with two intersections.Each of the two intersections is characterized via a characteristictemperature. The glass transition temperature T_(g) is obtained as theaverage of these two temperatures and the width of the glass transitionΔT_(g) is obtained from the difference between the two temperatures.

The microgels present in the inventive composition are known inprinciple and can be prepared in a manner known per se (see, forexample, EP-A-0 405 216, EP-A-0 854 171, DE-A 42 20 563, GB Patent1078400, DE-A-197 01 489, DE-A-197 01 488, DE-A-198 34 804, DE-A-198 34803, DE-A-198 34 802, EP-A-1 063 259, DE-A-199 39 865, DE-A-199 42 620,DE-A-199 42 614, DE-A-100 21 070, DE-A-100 38 488, DE-A-100 39 749,DE-A-100 52 287, DE-A-100 56 311 and DE-A-100 61 174).

The patent applications EP-A 405 216, DE-A-42 20 563 and also GB Patent1078400 describe the use of CR microgels, BR microgels and NBR microgelsin mixtures with double-bond-containing rubbers. DE-A-197 01 489describes the use of subsequently modified microgels in mixtures withdouble-bond-containing rubbers such as NR, SBR and BR.

The microgels which can be used in the inventive compositions areusually obtained via crosslinking of the following rubbers:

-   BR: polybutadiene,-   IR: polyisoprene,-   SBR: random styrene-butadiene copolymers with styrene contents of    1-60% by weight, preferably 5-50% by weight,-   X-SBR: carboxylated styrene-butadiene copolymers,-   FKM: fluororubber,-   ABR: butadiene-C₁₋₄-alkyl acrylate copolymers,-   ACM: acrylate rubber,-   NBR: nitrile rubbers, i.e. butadiene-acrylonitrile-co- or    terpolymers with acrylonitrile contents of 5-60% by weight,    preferably 10-50% by weight,-   X-NBR: carboxylated nitrile rubbers,-   CR: polychloroprene,-   IIR: isobutylene-isoprene copolymers with isoprene contents of    0.5-10% by weight,-   BIIR: brominated isobutylene-isoprene copolymers with bromine    contents of 0.1-10% by weight,-   CIIR: chlorinated isobutylene-isoprene copolymers with chlorine    contents of 0.1-10% by weight,-   HNBR: partially and fully hydrogenated nitrile rubbers,-   EPDM: ethylene-propylene-diene copolymers,-   EAM: ethylene-acrylate copolymers,-   EVM: ethylene-vinyl acetate copolymers,-   CO and ECO: epichlorohydrin rubbers,-   Q: silicone rubbers,-   AU: polyester urethane polymers,-   EU: polyether urethane polymers,-   ENR: epoxidized natural rubber or a mixture thereof.

The non-crosslinked microgel starting materials are advantageouslyprepared by emulsion polymerization.

It is also possible to use naturally occurring latices, e.g. naturalrubber latex.

The microgels used in the inventive composition are preferably thoseobtainable via emulsion polymerization and subsequent crosslinking.

When the inventively used microgels are prepared via emulsionpolymerization, examples of the monomers used, capable of free-radicalpolymerization, are the following:

Butadiene, styrene, acrylonitrile, isoprene, esters of acrylic andmethacrylic acid, tetrafluoroethylene, vinylidene fluoride,hexafluoropropene, 2-chlorobutadiene, 2,3-dichlorobutadiene, and alsodouble-bond-containing carboxylic acids, preferably acrylic acid,methacrylic acid, maleic acid or itaconic acid, double-bond-containinghydroxy compounds, preferably hydroxyethyl methacrylate, hydroxyethylacrylate or hydroxybutyl methacrylate, amine-functionalized acrylates,amine-functionalized methacrylates, acrolein, N-vinyl-2-pyrollidone,N-allylurea and N-allylthiourea, secondary amino(meth)acrylates, e.g.2-tert-butylaminoethyl methacrylate, and2-tert-butylaminoethylmethacrylamide.

The crosslinking of the rubber gel can be achieved directly during theemulsion polymerization process via copolymerization with polyfunctionalcompounds having crosslinking action, or else via subsequentcrosslinking as described below.

Direct crosslinking during the emulsion polymerization process ispreferred. Preferred polyfunctional comonomers are compounds having atleast 2, preferably from 2 to 4 copolymerizable C═C double bonds, e.g.diisopropenylbenzene, divinylbenzene, divinyl ether, divinyl sulphone,diallyl phthalate, triallyl cyanurate, triallyl isocyanurate,1,2-polybutadiene, N,N′-m-phenylenedimaleimide,N,N′-(4-methyl-m-phenylene)dimaleimide and/or triallyl trimellitate.Other compounds which can also be used are the acrylates andmethacrylates of polyhydric, preferably di- to tetrahydric C₂-C₁₀alcohols, e.g. ethylene glycol, 1,2-propanediol, 1,4-butanediol,1,6-hexanediol, neopentyl glycol, glycerol, trimethylolpropane,pentaerythritol and sorbitol. It is also possible to use acrylates andmethacrylates of polyethylene glycol having from 2 to 20, preferably 2to 8, oxyethylene units. It is also possible to use polyesters composedof aliphatic di- and/or polyols, or else maleic acid, fumaric acidand/or itaconic acid.

Crosslinking to give rubber microgels during the emulsion polymerizationprocess can also take place via continuation of the polymerizationprocess as far as high conversions or in the monomer feed process viapolymerization with high levels of internal conversion. Anotherpossibility is to carry out the emulsion polymerization process in theabsence of regulators.

For crosslinking of the non-crosslinked or weakly crosslinked microgelstarting products after the emulsion polymerization process, it is bestto use directly the latices obtained during the emulsion polymerizationprocess. This method can also be used to crosslink natural rubberlatices.

Crosslinking is carried out with suitable chemicals having crosslinkingaction. Examples of these suitable chemicals having crosslinking actionare

-   -   organic peroxides, such as dicumyl peroxide, tert-butyl cumyl        peroxide, bis(tert-butylperoxy-isopropyl)benzene, di-tert-butyl        peroxide, 2,5-dimethylhexane 2,5-dihydroperoxide,        2,5-dimethylhex-3-yne 2,5-dihydroperoxide, dibenzoyl peroxide,        bis(2,4-dichlorobenzoyl) peroxide, or tert-butyl perbenzoate,    -   organic azo compounds, such as azobisisobutyronitrile or        azobiscyclohexane nitrile, and also    -   di- or polymercapto compounds, such as dimercaptoethane,        1,6-dimercaptohexane, 1,3,5-trimercaptotriazine or        mercapto-terminated polysulphide rubbers, such as        mercapto-terminated reaction products of bischloroethyl formal        with sodium polysulphide.

The ideal temperature for conducting the post-crosslinking processnaturally depends on the reactivity of the crosslinking agent; it can becarried out at temperatures of from 20° C. to about 180° C., ifappropriate at elevated pressure (see in this connection Houben-Weyl,Methoden der organischen Chemie [Methods of organic chemistry], 4thEdition, Vol. 14/2, page 848).

Particularly preferred crosslinking agents are peroxides.

The crosslinking of rubbers containing C═C double bonds to givemicrogels can also take place in dispersion or emulsion withsimultaneous, partial to, if appropriate, complete hydrogenation of theC═C double bond via hydrazine (as described in U.S. Pat. No. 5,302,696or U.S. Pat. No. 5,442,009) or, if appropriate, other hydrogenatingagents, such as organometal hydride complexes.

Prior to, during or after the post-crosslinking process it is possible,if appropriate, to carry out a particle enlargement process viaagglomeration.

The abovementioned preparation process for the microgels preferably doesnot give completely homogeneously crosslinked microgels.

Microgels used for the inventive composition can be either modifiedmicrogels which have functional groups, and in particular specificallyat the surface, or else can be unmodified microgels which in essencehave no reactive groups, and in particular specifically none at thesurface.

The modification of the microgels can take place either via grafting ofthe microgels with functional monomers or else via reaction withlow-molecular-weight agents.

The aim of the microgel modification is improvement in compatibility ofthe microgel with the matrix, in order to achieve good dispersibilityduring preparation and also good coupling to the matrix.

For grafting of the microgels with functional monomers it isadvantageous to start from the aqueous microgel dispersion, which isreacted with polar monomers, such as acrylic acid, methacrylic acid,itaconic acid, hydroxyethyl(meth)acrylate, hydroxypropyl(meth)acrylate,hydroxybutyl(meth)acrylate, acrylamide, methacrylamide, acrylonitrile,acrolein, N-vinyl-2-pyrollidone, N-allylurea or N-allylthiourea, or elsesecondary amino(meth)acrylates, such as 2-tert-butylaminoethylmethacrylate, and 2-tert-butylaminoethylmethacrylamide, under theconditions of free-radical emulsion polymerization. This method givesmicrogels with core/shell morphology, the intention being that the shellhas high compatibility with the matrix. It is desirable that thegrafting of the monomer used in the modification step onto theunmodified microgel is as quantitative as possible. The functionalmonomers are advantageously metered into the mixture prior to thecomplete crosslinking of the microgels.

Modified microgels having functional groups can moreover be prepared viachemical reaction of the previously crosslinked microgels withlow-molecular-weight agents reactive towards C═C double bonds. Thesereactive chemicals are in particular compounds which can cause chemicalbonding of polar groups, e.g. aldehyde groups, hydroxy groups, carboxygroups, nitrile groups, etc., or else sulphur-containing groups, e.g.mercapto groups, dithiocarbamate groups, polysulphide groups,xanthogenate groups, thiobenzothiazole groups and/or dithiophosphoricacid groups and/or unsaturated dicarboxylic acid groups, to themicrogels. This also applies to N,N′-m-phenylenediamine.

Examples of suitable agents are:

Hydrogen sulphide and/or alkyl polymercaptans, such as1,2-dimercaptoethane or 1,6-dimercaptohexane, and also dialkyl- and/ordialkylaryldithiocarbamate, e.g. the alkali metal salts ofdimethyldithiocarbamic acid and/or dibenzyldithiocarbamic acid, and alsoalkyl and/or aryl xanthogenates, such as potassium ethyl xanthogenateand sodium isopropyl xanthogenate, the alkali metal or alkaline earthmetal salts of dibutyl dithiophosphoric acid, dioctyl dithiophosphoricacid and/or dodecyl dithiophosphoric acid. The reactions mentioned canadvantageously also be carried out in the presence of sulphur, and thesulphur here is concomitantly incorporated with formation ofpolysulphidic bonds. For the addition reaction with this compound,free-radical initiators can be added, e.g. organic and/or inorganicperoxides and/or azo initiators.

Modification of double-bond-containing microgels for example viaozonolysis or else via halogenation with chlorine, bromine and iodine isalso possible. Further reaction of modified microgels, e.g. preparationof hydroxy-group-modified microgels from epoxidized microgels, is alsoregarded as chemical modification of microgels.

In one preferred embodiment, the microgels have been modified viahydroxy groups, and also in particular at the surface. The hydroxy groupcontent of the microgels in the form of hydroxy number whose dimensionis mg KOH/g of polymer is determined via reaction of acetic anhydrideand titration of the resultant acetic acid liberated with KOH to DIN53240. The hydroxy number of the microgels is preferably in the rangefrom 0.1 to 100 mg KOH/g of polymer and particularly preferably in therange from 0.5 to 50 mg KOH/g of polymer.

The amount of the modifier used depends on its activity and on therequirements set in a particular instance and is in the range from 0.05to 30% by weight, based on the total amount of rubber microgel used,particularly preferably in the range from 0.5 to 10% by weight, based onthe total amount of rubber microgel used.

The modification reactions can be carried out at temperatures of 0-180°C., preferably 20-95° C., if appropriate under pressure of 1-30 bar. Themodifications can be undertaken on rubber microgels in bulk or in theform of their dispersion, and in the latter instance here a reactionmedium used may comprise inert organic solvents or else comprise water.The modification is particularly preferably carried out in aqueousdispersion of the crosslinked rubber.

The average diameter of the microgels prepared can be adjusted with highprecision for example to 0.1 micrometer (100 nm)±0.01 micrometer (10nm), thus, for example, achieving a particle size distribution in whichthe size of at least 75% by weight of all of the microgel particles isfrom 0.095 micrometer to 0.105 micrometer. Examples of other feasibleaverage diameters of the microgels are in the range from 5 to 500 nmwith the same precision of preparation and use (meaning that at least75% by weight of all of the particles are within a range of ±10% aboveand below the maximum of the cumulative grain size distribution curve(determined via ultracentrifugation)). The morphology of the dispersedmicrogels in the inventive composition can thus be adjusted topractically exactly as required, thus correspondingly influencing theproperties of the inventive composition and also of the vulcanisatesprepared therefrom by way of example. Particularly fine-particlemicrogels are prepared via emulsion polymerization via control of thereaction parameters in a manner known per se (see, for example, B. H. G.Elias, Makromoleküle [Macromolecules], Volume 2, Technologie[Technology], 5th Edition, 1992, pages 99 ff.).

The resultant microgels can be worked up by way of example viaevaporated concentration or via coagulation or via co-coagulation withanother latex polymer, or via freeze coagulation (cf. U.S. Pat. No.2,187,146) or via spray drying. In the case of work-up via spray dryingit is also possible to add commercially available flow aids, such asCaCO₃ or silica.

In one preferred embodiment, the inventive vulcanizable compositioncomprises

-   -   a) 100 parts by weight of one or more hydrogenated nitrile        rubbers,    -   b) from 1 to 100 parts by weight, preferably from 5 to 80 parts        by weight,        -   of one or more unsaturated mono- or dicarboxylic acids            having from 3 to 10 carbon atoms and/or of one or more salts            thereof, preferably zinc diacrylate or zinc methacrylate,    -   c) from 0.2 to 8 parts by weight, preferably from 0.2 to 5 parts        by weight, particularly preferably from 0.2 to 4 parts by        weight,        -   of one or more peroxides, preferably dicumyl peroxide,            tert-butyl cumyl peroxide,            bis(tert-butylperoxyisopropyl)benzene, di-tert-butyl            peroxide, 2,5-dimethylhexane 2,5-dihydroperoxide,            2,5-dimethylhex-3-yne 2,5-dihydroperoxide or dibenzoyl            peroxide,    -   d) from 5 to 60 parts by weight, preferably from 10 to 50 parts        by weight,        -   of one or more microgels, preferably a BR or SBR microgel,            whose glass transition temperature T_(g) is below −20° C.,            preferably whose glass transition temperature T_(g) is below            −50° C. and    -   e) from 0 to 100 parts by weight, preferably from 5 to 80 parts        by weight,        -   of one or more conventional rubber additives, preferably one            or more fillers, in particular carbon black, silica, zinc            oxide, magnesium oxide or aluminium oxide, of one or more            filler activators, in particular based on an organic silane,            of one or more antioxidants, in particular oligomerized            2,2,4-trimethyl-1,2-dihydroquinoline (TMQ), styrenated            diphenylamine (DDA), octylated diphenylamine (OCD) or zinc            salt of 4- and 5-methylmercaptobenzimidazole (ZMB2) and/or            of one or more mould-release agents.

Among conventional rubber additives are, by way of example:

Fillers, filler activators, accelerators, polyfunctional crosslinkingagents, ozone stabilizers, antioxidants, processing oils, extender oils,plasticizers, activators, and also scorch inhibitors. It is alsopossible to reinforce the vulcanisates with reinforcement materialscomposed of glass according to the teaching of U.S. Pat. No. 4,826,721,or else to use aromatic polyamides (Aramid®) for reinforcement.

Examples of fillers that can be used are carbon black, silica, bariumsulphate, titanium dioxide, zinc oxide, calcium oxide, calciumcarbonate, magnesium oxide, aluminium oxide, iron oxide, diatomaceousearth or silicates.

Particular filler activators that can be used are organic silanes, e.g.vinyltrimethyloxysilane, vinyldimethoxymethylsilane,vinyltriethoxysilane, vinyltris(2-methoxyethoxy)silane,N-cyclohexyl-3-aminopropyltrimethoxysilane,3-aminopropyltrimethoxysilane, methyltrimethoxysilane,methyltriethoxysilane, dimethyldimethoxysilane, dimethyldiethoxysilane,trimethylethoxysilane, isooctyltrimethoxysilane,isooctyltriethoxysilane, hexadecyltrimethoxysilane or(octadecyl)methyldimethoxysilane. Examples of other filler activatorsare surfactant substances such as triethanolamine or ethylene glycolswith molar masses of from 74 to 10 000 g/mol. The amount of filleractivators is usually from 0.5 to 10 parts by weight, based on 100 phrof the hydrogenated nitrile rubber.

Antioxidants that can be used are in particular those giving minimumscavenging of free radicals during peroxidic vulcanization. These are inparticular oligomerized 2,2,4-trimethyl-1,2-dihydroquinoline (TMQ),styrenated diphenylamine (DDA), octylated diphenylamine (OCD) or thezinc salt of 4- and 5-methylmercaptobenzimidazole (ZMB2). Alongsidethese, it is also possible to use the known phenolic antioxidants,examples being sterically hindered phenols or antioxidants based onphenylenediamine. It is also possible to use combinations of theantioxidants mentioned.

The amounts usually used of the antioxidants are from 0.1 to 5 parts byweight, preferably from 0.3 to 3 parts by weight, based on the totalamount of polymer.

Examples of mould-release agents that can be used are: saturated orpartially unsaturated fatty and oleic acids or their derivatives (in theform of fatty acid esters, fatty acid salts, fatty alcohols or fattyacid amides) and also products that can be applied to the mould surface,e.g. products based on low-molecular-weight silicone compounds, productsbased on fluoropolymers, and also products based on phenolic resins.

The amounts used of the mould-release agents as constituent of themixture are from 0.2 to 10 parts by weight, preferably from 0.5 to 5parts by weight, based on the total amount of polymer.

The invention further provides a process for preparation of theabovementioned vulcanizable compositions, by mixing components a, b, cand d, and also, if appropriate, e with one another. This can take placewith use of apparatuses and mixing devices known to the person skilledin the art.

The invention further provides the production of vulcanized products byexposing the inventive vulcanizable compositions to heat treatment.

The vulcanized products are produced by exposing the inventivevulcanizable compositions in a conventional manner in suitable moulds toa temperature in the range which is preferably from 120 to 200° C.,particularly preferably from 140 to 180° C.

The invention therefore also provides the vulcanized products obtainablevia vulcanizing of the inventive compositions.

These vulcanized products are preferably drive belts, roll coverings,gaskets, hoses and cables.

The principles of production of these drive belts, roll coverings,gaskets, hoses and cables are known to the person skilled in the art.For production of drive belts, the person skilled in the art can proceedby way of example by analogy with the disclosure of U.S. Pat. No.4,715,607, using the inventive vulcanizable compositions.

EXAMPLES

Preparation Examples for the Microgels:

The preparation of the microgels used in the remaining examples isdescribed below.

Microgels A and B were prepared via emulsion polymerization, using thefollowing monomers: butadiene, styrene, trimethylolpropanetrimethacrylate (TMPTMA) and hydroxyethyl methacrylate (HEMA). Themonomers used for preparation of the microgels, and also substantialconstituents of the mixing specification, have been collated in Table 1below: TABLE 1 Composition of microgels A and B used EmulsifiersMonomers Water Mersolat TCD²⁾ TMPTMA HEMA Initiation ActivationTermination K30/95¹⁾ (20%) Butadiene Styrene (90%) (96%) Microgel [g][g] [g] [g] [g] [g] [g] [g] [g] A 12608 287 530 137 250 3805.5 0 172322.5 (Tg = −75° C.) B 13742 251 125 137 250 2740.5 304.5 105 350.0 (Tg= −65° C.)¹⁾Mersolat ® K 30/95 (Lanxess Deutschland GmbH): Isomeric mixture of thesodium salts of long-chain alkylsulphonic acids. Content of activesubstance is 95% by weight.²⁾TCD Sodium salt of reaction product of bishydroxyformylateddicyclopentadiene with hexahydrophthalic anhydride. An aqueous solutionis used with 20% by weight of active substance. (The emulsifier wasprepared according to US-A-5,100,945).

For preparation of the microgels, the amounts stated in Table 1 of theemulsifiers Mersolat® K30/95 and TCD were first dissolved in water andused as initial charge in a 40 l autoclave. The autoclave was evacuatedthree times and treated with nitrogen. The monomers stated in Table 1were then added. The monomers were emulsified in the emulsifier solutionat 30° C., with stirring.

An aqueous solution composed of 171 g of water, 1.71 g ofethylenediaminetetraacetic acid (Merck-Schuchardt), 1.37 g of ferroussulphate*7H₂O, 3.51 g of sodium formaldehyde-sulphoxylate hydrate(Merck-Schuchardt), and also 5.24 g of trisodium phosphate*12H₂O wasthen metered in. The amount of water used for this is stated in thecolumn “Initiation” in Table 1.

The reaction was initiated via addition of 5.8 g of p-menthanehydroperoxide, 50% (Trigonox® NT 50 from Akzo-Degussa), which wasemulsified by means of 10.53 g of Mersolat® K30/95 in half of the amountof water listed in the “Activation” column.

After 2.5 hours of reaction time, the reaction temperature was increasedto 40° C. After another hour of reaction time, post-activation wascarried out using an amount of initiator solution (Trigonox®NT50/water/Mersolat® K30/95) identical with that used for initiation ofthe polymerization process. The polymerization temperature was increasedto 50° C. here.

On reaching >95% polymerization conversion, the polymerization processwas terminated via addition of 23.5 g of diethylhydroxylamine. For this,diethylhydroxylamine was dissolved in the amount of water listed in the“Termination” column in Table 1.

Unreacted monomers were then removed from the latex via steam-stripping.The latex was filtered and, as in Example 2 of U.S. Pat. No. 6,399,706,stabilizer was admixed with the mixture, which was coagulated and dried.

The gels were characterized both in the latex state by means ofultracentrifugation (diameter and specific surface area) and also in theform of solid product with respect to solubility in toluene (gelcontent, swelling index/SI), via acidimitric titration (OH number andCOOH number) and by means of DSC (glass transition temperature/T_(g) andwidth of T_(g) transition).

The characteristic data for the microgels have been collated in Table 2below: TABLE 2 Properties of microgels A and B Gel OH Acid Diametercontent number number d₁₀ d_(z) d₈₀ SA_(spec.) [% by Tg ΔTg [mg_(KOH)/[mg_(KOH)/ Microgel [nm] [nm] [nm] [m²/g] wt.] SI [° C.] [° C.]g_(pol.)] g_(pol.)] A 43.5 50.9 55.7 127 91.7 13.1 −75 15.2 33 7.4 B35.4 48.2 55.1 139 94.8 7.4 −65.5 12 37.8 8.6

In Table 2:

-   SA_(spec.): is specific surface area in m²/g-   d_(z): The diameter d _(z), is according to DIN 53 206 defined as    the median or central value above and below which in each case half    of all of the particle sizes lies. The particle diameter of the    latex particles is determined by means of ultracentrifugation (W.    Scholtan, H. Lange, “Bestimmung der Teilchengröβenverteilung von    Latices mit der Ultrazentrifuge” [Determination of particle size    distribution of latices using the ultracentrifuge],    Kolloid-Zeitschrift und Zeitschrift für Polymere (1972) Volume 250,    No. 8). The diameter data in the latex and for the primary particles    in the inventive compositions are practically identical, since the    particle size of the microgel particles exhibits practically no    change during preparation of the inventive composition.-   d₁₀ and d₈₀: The diameter data d₁₀ and d₈₀ indicate that the    diameter of respectively 10 and 80% by weight of the particles is    smaller than the stated value, the particle size distribution here    being determined by means of ultracentrifugation.    -   The diameter data in the latex and for the primary particles in        the inventive compositions are practically identical, since the        particle size of the microgel particles exhibits practically no        change during preparation of the inventive composition.-   T_(g): Glass transition temperature. This was determined as    mentioned above in the application.-   ΔT_(g): Width of T_(g) transition    -   This was determined as mentioned above in the application.    -   Perkin-Elmer DSC-2 equipment is used for determination of T_(g)        and ΔT_(g).-   SI: is swelling index.    -   This was determined as follows:    -   The swelling index is calculated from the weight of the        solvent-containing microgel swollen for 24 hours in toluene at        23° and the weight of the dry microgel:        SI=wet weight of microgel/dry weight of microgel    -   To determine the swelling index, 250 mg of the microgel are        swollen in 25 ml of toluene for 24 h, with shaking. The        toluene-swollen (wet) gel is weighed after centrifuging at 20        000 rpm and then dried at 70° C. to constant weight and again        weighed.-   OH number: is hydroxy number    -   The OH number is determined to DIN 53240 and corresponds to the        amount of KOH in mg equivalent to the amount of acetic acid        liberated during acetylation of 1 g of substance, using acetic        anhydride.-   Acid number: The acid number is determined as mentioned above to DIN    53402 and corresponds to the amount of KOH in mg required to    neutralize 1 g of the polymer.-   Gel content: The gel content corresponds to the fraction insoluble    in toluene at 23° C. It is determined as described above.    Preparation, Vulcanization and Characterization of Rubber Mixtures

An internal mixer of capacity 1.5 l with intermeshing rotor geometry(Werner & Pfleiderer GK1.5E) was used to prepare the rubber mixtures.First, the hydrogenated nitrile rubber was added to the mixer. After 30s, gel and zinc diacrylate were added and mixed at a constant rotorrotation rate of 40 rpm. After 4 min of mixing time, the mixture wasdischarged. After a storage time of 24 h, the mixture was again mixed at40 rpm for 4 min. Perkadox® 14-40 B-GR, Vulkanox® ZMB2/5 and Rhenofit®DDA-70 were then incorporated by mixing on the roll at 40° C.

Examples 1-3 below are comparative examples, while Examples 4 and 5 areinventive examples. TABLE 3 Composition of rubber mixtures in parts byweight Rubber mixtures 1 2 3 4 5 Therban ® A 3406 ¹⁾ 100 100 100 100 100Microgel A 0 0 0 10 0 Microgel B 0 0 0 0 10 Saret ® SR633 ²⁾ 60 70 80 6060 Perkadox ® 14-40 B-GR ³⁾ 4 4 4 4 4 Vulkanox ® ZMB2/5 ⁴⁾ 0.8 0.8 0.80.8 0.8 Rhenofit ® DDA-70 ⁵⁾ 2 2 2 2 2The following were used in Table 3:¹⁾ Hydrogenated nitrile rubber from Lanxess Deutschland GmbH with 34% byweight of acrylonitrile, ML (1 + 4@100° C.) = 77; residual double bondcontent: 3.5%²⁾ Zinc diacrylate from Sartomer³⁾ Dicumyl peroxide from Akzo in pellet form with 40% active ingredientcontent⁴⁾ Zinc methylmercaptobenzimidazole from Lanxess Deutschland GmbH⁵⁾ Octylated diphenylamine with 70% by weight active ingredient contentfrom RheinChemie Rheinau GmbH

The values stated in Table 4 were determined on the unvulcanizedcompounded materials: TABLE 4 Properties of unvulcanized rubber mixturesProperties of compounded material: 1 2 3 4 5 Mooney [ME] 40 37 32 39 42viscosity (ML1 + 4/100° C.) to ASTM D1646 Mooney [%] 6.7 6.9 7.4 6 7.4relaxation (MR) to ISO 289, Part 4

The results show that the inventive rubber mixtures (4 and 5) arecomparable in terms of Mooney viscosity and Mooney relaxation with thereference vulcanisates (1, 2 and 3).

The vulcanization performance of the mixtures was studied to ASTM D5289at 180° C. with the aid of the MDR2000 Moving Die Rheometer from AlphaTechnology. The characteristic vulcameter values F_(a), F_(max),F_(max)−F_(a), t₁₀, t₅₀, t₉₀ and t₉₅ were thus determined. TABLE 5Vulcanization performance of rubber mixtures Mixture No.: 1 2 3 4 5F_(a) [dNm] 1.7 1.4 1.5 0.6 1.8 F_(max) [dNm] 29.3 32.5 39 31 31.4F_(max) − F_(a) [dNm] 27.6 31.1 37.5 30.4 29.6 t₁₀ [min] 0.8 0.9 0.950.9 0.8 t₅₀ [min] 1.3 1.3 1.4 1.3 1.3 t₉₀ [min] 5.1 4.6 4.7 4.7 5.3 t₉₅[min] 6.9 6.3 6.4 6.9 7.5

According to DIN 53 529, Part 3:

-   F_(a): is the indicated vulcameter value at the minimum of the    crosslinking isotherm-   F_(max): is the maximum indicated vulcameter value-   F_(max)−F_(a): is the difference between maximum and minimum of the    indicated vulcameter values-   t₁₀: is the juncture at which 10% of final conversion has been    achieved-   t₅₀: is the juncture at which 50% of final conversion has been    achieved-   t₉₀: is the juncture at which 90% of final conversion has been    achieved-   t₉₅: is the juncture at which 95% of final conversion has been    achieved

The series of experiment shows that the inventively prepared rubbermixtures (4 and 5) have vulcanization performance comparable with thatof the reference mixtures (1, 2 and 3).

The rubber mixtures were then vulcanized for 9 min at 180° C. at apressure of 170 bar in a platen press. The test values stated in Table 6were determined on the unaged vulcanisates at 23° C. TABLE 6 Propertiesof vulcanized rubber mixtures at 23° C. Vulcanisate properties at 23° C.(without ageing) 1 2 3 4 5 Shore A [ShA] 75 74 78 79 77 hardness DIN53505 DIN 53512 [%] 48 46 46 48 47 rebound resilience DIN 53516 [mm³] 6683 107 70 79 abrasion DIN 53504 [%] 399 417 410 357 372 tensile strainat break (ε_(b)) DIN 53504 [MPa] 25.7 22.3 19.9 27 24.0 ultimate tensilestrength (σ_(max.)) DIN 53504 [MPa] 2.2 2.3 2.6 2.7 2.5 tensile stressat 25% tensile strain (σ₂₅) DIN 53504 [MPa] 5.2 5.8 6.3 6.4 6.2 tensilestress at 100% tensile strain (σ₁₀₀) DIN 53504 [MPa] 15.8 14.3 14.0 21.317.8 tensile stress at 300% tensile strain (σ₃₀₀)

The series of experiment shows that the inventively preparedvulcanisates (4 and 5) are at least equivalent to the referencevulcanisates (1, 2 and 3) in terms of Shore A hardness, reboundresilience and abrasion.

The test values stated in Table 7 were also determined on the unagedspecimens at 130° C. TABLE 7 Properties of vulcanized rubber mixtures at130° C. Vulcanisate properties at 130° C. (without ageing) 1 2 3 4 5 DIN53504 [%] 184 171 169 187 168 tensile strain at break (ε_(b)) DIN 53504[MPa] 4.8 3.7 3.7 5 4.5 ultimate tensile strength (σ_(max.)) DIN 53504[MPa] 1.4 1.2 1.5 1.6 1.6 tensile stress at 25% tensile strain (σ₂₅) DIN53504 [MPa] 3.3 2.9 3.5 3.5 3.7 tensile stress at 100% tensile strain(σ₁₀₀) σ₂₅ × ε_(b) [MPa] × [%] 258 205 233 299 268 σ₁₀₀ × ε_(b) [MPa] ×[%] 607 496 592 655 622

The series of experiment shows that the inventively preparedvulcanisates (4 and 5) are slightly superior to the referencevulcanisates (1, 2 and 3) with respective to ultimate tensile strengthand are markedly superior with respect to the product σ₂₅×ε_(b) andσ₁₀₀×ε_(b).

To characterize ageing performance, all of the vulcanisates were thenaged at 150° C. for 7 days to DIN 53508.

The values stated in Table 8 were then determined at a test temperatureof 130° C. TABLE 8 Properties of vulcanized rubber mixtures after ageingat 150° C./7 days (test temperature: 130° C.) Vulcanisate properties at130° C. (after 7 days ageing at 150° C.) 1 2 3 4 5 DIN 53504 [%] 158 168149 148 145 tensile strain at break (ε_(b)) DIN 53504 [MPa] 5.6 5.6 5.86 5.8 ultimate tensile strength (σ_(max.)) DIN 53504 [MPa] 1.8 1.8 2.12.2 2.2 tensile stress at 25% tensile strain (σ₂₅) DIN 53504 [MPa] 4.24.2 4.6 5.0 5.1 tensile stress at 100% tensile strain (σ₁₀₀) σ₂₅ × ε_(b)[MPa] × [%] 284 302 313 326 319 σ₁₀₀ × ε_(b) [MPa] × [%] 664 705 685 740740

The series of experiment shows that the inventively preparedvulcanisates (4 and 5) are superior to the reference vulcanisates (1, 2and 3) with respect to the product σ₂₅×ε_(b) and σ₁₀₀×ε_(b) after 7 daysof hot-air ageing at 150° C. (test temperature: 130° C.).

Each of the physical parameters was determined according to the relevantDIN specifications. Supplementary reference is made to Kleemann, Weber,Formeln und Tabellen für die Elastomerverarbeitung [Formulae and tablesfor elastomer processing], Dr Gupta Verlag, 1994.

1. A vulcanizable composition comprising a) one or more hydrogenatednitrile rubbers, b) one or more unsaturated carboxylic acids and/or oneor more salts thereof, c) at least one peroxide and d) at least onemicrogel whose glass transition temperature is below −20° C.
 2. Thevulcanizable composition according to claim 1, wherein the component a)used comprises one or more hydrogenated nitrile rubbers which are co- orterpolymers based on at least one conjugated diene and on at least oneα,β-unsaturated nitrile monomer and also if appropriate on othercopolymerizable monomers, in which the diene units incorporated into thepolymer have been entirely or to some extent hydrogenated.
 3. Thevulcanizable composition according to claim 1 or 2, wherein thecomponent a) used comprises one or more hydrogenated nitrile rubbers inwhich the Mooney viscosity (ML 1+4 @ 100° C.) is in the range from 10 to120 MU, where the Mooney viscosity is determined to ASTM standard D1646.4. The vulcanizable composition according to claim 1 or 2, wherein thecomponent a) used comprises one or more hydrogenated nitrile rubbers inwhich the Mooney viscosity (ML 1+4 @ 100° C.) is in the range from 15 to100 MU, where the Mooney viscosity is determined to ASTM standard D1646.5. The vulcanizable composition according to claim 1 or 2, wherein thecomponent b) used comprises one or more unsaturated carboxylic acidsand/or one or more salts thereof and the unsaturated carboxylic acid canbe an α,β-ethylenically unsaturated mono- or dicarboxylic acid havingfrom 3 to 10 carbon atoms.
 6. The vulcanizable composition according toclaim 1 or 2, wherein the component b) used comprises one or moreunsaturated carboxylic acids and/or one or more salts thereof and theunsaturated carboxylic acid is selected from the group consisting ofmethacrylic acid, acrylic acid, cinnamic acid, crotonic acid anditaconic acid and the salts are selected from the group consisting ofsodium, potassium, magnesium, calcium, zinc, barium, aluminium, tin,zirconium and lithium.
 7. The vulcanizable composition according toclaim 1 or 2, wherein the component b) used comprises one or more metaldiacrylates and/or metal dimethacrylates.
 8. The vulcanizablecomposition according to claim 1 or 2, wherein the component b) usedcomprises zinc diacrylate or zinc dimethacrylate.
 9. The vulcanizablecomposition according to claim 1 or 2, wherein the component c) usedcomprises at least one peroxide.
 10. The vulcanizable compositionaccording to claim 1 or 2, wherein the component c) used comprises atleast one peroxide selected from the group consisting of dicumylperoxide, tert-butyl cumyl peroxide,bis(tert-butylperoxyisopropyl)benzene, di-tert-butyl peroxide,2,5-dimethylhexane 2,5-dihydroperoxide, 2,5-dimethylhex-3-yne2,5-dihydroperoxide, dibenzoyl peroxide,bis(2,4-dichlorobenzoyl)peroxide, tert-butyl perbenzoate, butyl4,4-di(tert-butylperoxy)valerate and1,1-bis(tert-butylperoxy)-3,3,5-trimethylcyclohexane.
 11. Thevulcanizable composition according to claim 1 or 2, wherein thecomponent d) used comprises at least one microgel whose glass transitiontemperature is below −20° C. and which is a crosslinked homopolymer orcrosslinked random copolymer.
 12. The vulcanizable composition accordingto claim 1 or 2, wherein the component d) used comprises at least onemicrogel whose glass transition temperature is below −20° C. and whichhas at least 70% by weight of fractions (“gel content”) insoluble intoluene at 23° C.
 13. The vulcanizable composition according to claim 1or 2, wherein the component d) used comprises at least one microgelwhose glass transition temperature is below −20° C. and which has aswelling index (“SI”) in toluene at 23° C. of less than 80, where theswelling index is calculated from the weight of the solvent-containingmicrogel swollen for 24 hours in toluene at 23° C. (after centrifugingat 20 000 rpm) and the weight of the dry microgel by using the followingformula:SI=wet weight of microgel/dry weight of microgel.
 14. The vulcanizablecomposition according to claim 1 or 2, wherein the component d) usedcomprises at least one microgel whose glass transition temperature is inthe range from −100° C. to −20° C.
 15. The vulcanizable compositionaccording to claim 1 or 2, wherein the component d) used comprises atleast one microgel whose glass transition temperature is below −20° C.and which has been selected from the group consisting of BR(polybutadiene), IR (polyisoprene), SBR (random styrene-butadienecopolymers with styrene contents of 1-60% by weight, preferably 5-50% byweight), X-SBR (carboxylated styrene-butadiene copolymers), FKM(fluororubber), ABR (butadiene-C1-4-alkyl acrylate copolymers), ACM(acrylate rubber), NBR (butadiene-acrylonitrile copolymers withacrylonitrile contents of 5-60% by weight, preferably 10-50% by weight),X-NBR (carboxylated nitrile rubbers), CR (polychloroprene), IIR(isobutylene-isoprene copolymers with isoprene contents of 0.5-10% byweight), BIIR (bromated isobutylene-isoprene copolymers with brominecontents of 0.1-10% by weight), CIIR (chlorinated isobutylene-isoprenecopolymers with chlorine contents of 0.1-10% by weight), HNBR (partiallyand/or fully hydrogenated nitrile rubbers), EPDM(ethylene-propylene-diene copolymers), EAM (ethylene-acrylatecopolymers), EVM (ethylene-vinyl acetate copolymers), CO and ECO(epichlorohydrin rubbers), Q (silicone rubbers), AU (polyester urethanepolymers), EU (polyether urethane polymers), ENR (epoxidized naturalrubber) and mixtures thereof.
 16. The vulcanizable composition accordingto claim 1 or 2, comprising a) 100 parts by weight of one or morehydrogenated nitrile rubbers, b) from 1 to 100 parts by weight of one ormore unsaturated mono- or dicarboxylic acids having from 3 to 10 carbonatoms and/or of one or more salts thereof, c) from 0.2 to 8 parts byweight of one or more peroxides, d) from 5 to 60 parts by weight of oneor more microgels, whose glass transition temperature T_(g) is below−20° C. and e) from 0 to 100 parts by weight of one or more conventionalrubber additives.
 17. A process for the preparation of the vulcanizablecompositions according to claims 1 or 2, wherein the components a, b, cand d are mixed with one another.
 18. A process for the production ofvulcanized products, wherein the vulcanizable composition according toclaim 1 or 2 is exposed to heat treatment.
 19. The process according toclaim 14, wherein the vulcanizable composition according to claim 1 or 2is exposed in moulds to a temperature in the range from 120 to 200° C.20. A vulcanized product obtainable by the process of claim 19 or 20.21. The vulcanized product according to claim 20 in the form of a drivebelt, a roll covering, a gasket, a hose or a cable.